Scientists Identify an Orangutan Species That May be the Rarest Great Ape on Earth

Fagjun | Published 2017-11-15 11:06

A tiny orangutan population living in Sumatra has turned out to be the newest orangutan species known to science. Though newly discovered, this species is already considered to be critically endangered, and is the rarest known great ape species on the planet.

A newly-identified orangutan species



Prior to this discovery, there were two known species of orangutan: the Pongo pygmaeus (Bornean) and the Pongo abelii (Sumatran). Now, there are three. While the identification of a new orangutan and great ape species seems like a cause for celebration, scientists may actually be in a race against time to save this new species. At present, there are only about 800 of these orangutans in the wild, threatened by habitat loss as well as the illegal wildlife trade.


These new orangutans live only in the forest of Batang Toru on the island of Sumatra. For years, the existence of these orangutans has puzzled scientists. Now, however, these scientists have their answers.

The Tapanuli Orangutans

Tapanuli orangutans have a distinct hair color and texture. [Photo by Andrew Walmsley/Sumatra Orangutan Conservation Programme/Body Shop]



Michael Krützen, a geneticist, has been studying these great apes for more than ten years. According to Krützen, he had always thought that this small group of orangutans were Pongo abelii, since the population of Pongo abelii orangutans lived just on the same island. However, the new species, named the Tapanuli orangutans, turned out to be genetically distinct from their neighbors. In fact, the Tapanuli orangutans were so genetically distinct that they were more closely related to their cousins across the water on Borneo.


According to a new study, the three different species come from three different evolutionary lineages. Interestingly enough, the newest species to be discovered has turned out to be from the oldest lineage.


The physically distinct skull of a Tapanuli orangutan [Photo by Nater et al]



Back in 2013, the Sumatran Orangutan Conservation Program received a call about a male orangutan in the Tapanuli region. The ape, unfortunately, had cuts all over his body as well as air rifle pellets--evidence of abuse by humans. Despite the ensuing medical intervention for the orangutan, he died eight days after his rescue.


However, he lived on in scientific research, since his remains aided researchers in discovering the existence of his species. Studying this orangutan’s skull and jaws compared to those of 33 other male orangutans led researchers to the discovery of the Tapanuli orangutan species.

DNA Evidence

A diagram of the three orangutan species [Image by UZH]



Researchers found that the skull of the male Tapanuli orangutan was smaller than the skulls of Sumatran and Bornean males. The calls of the Tapanuli orangutans were also different, and their fur was more of a cinnamon color and was quite frizzier. Dominant male Tapanuli orangutans also sported mustaches, while females sported beards.


An analysis of the nuclear and mitochondrial DNA of all three orangutan species also revealed some interesting things. The mitochondrial DNA of Tapanuli orangutans is similar to that of Bornean orangutans, while the nuclear DNA of Tapanuli orangutans is similar to that of Sumatran orangutans. This indicates that the three species actually interbred with each other throughout the generations.


The Bornean and Sumatran orangutans, like their newly-identified cousins, are also critically endangered. However, with the identification of the Tapanuli species, there’s a better chance that it will be recognized and protected as well.

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